Mesh deformed after rigging?
Saying that the face "scales" when moved is uncorrect. Instead, mesh is deforming in a different way than expected. The reason lies in weighting, as some vertices are assigned only to the "face" bone while others are assigned both to "face" and "head" bones, as shown in the picures.





"A" vertex is the "correct one, as it follows exactly the face bone: face bone is child of the head bone, so the "face" vertices are moving without the need to be assigned also to the head bone: this double assignement is leading to the unexpected behaviours: double assignement (or even triple, or more) is OK only in proximity of joints, where you want the mesh to deform and stretch to get better creases and wrinkles.